This invention relates to communications on computer networks. More specifically, it relates to a method and system for tunnel optimized call setup for mobile nodes that have roamed from a home network to a foreign network.
The Internet Protocol (xe2x80x9cIPxe2x80x9d) is an addressing protocol designed to route traffic within a network or between networks. The Internet Protocol is used on many computer networks including the Internet, intranets and other networks. Internet Protocol addresses are typically assigned to xe2x80x9cimmobilexe2x80x9d nodes on a network. An immobile node may be moved to a different computer network, but is typically associated with a static physical location (e.g., 3Com Corporation in Santa Clara, Calif.) and an immobile Internet protocol address.
The Mobile-Internet Protocol (hereinafter Mobile IP) allows xe2x80x9cmobilexe2x80x9d nodes to transparently move between different Internet Protocol sub-networks (xe2x80x9csubnetsxe2x80x9d). Internet Protocol addresses are typically assigned to mobile nodes based on their home Internet Protocol subnet. The home subnet is connected to an external network (e.g., the Internet or an intranet) with a xe2x80x9chome agentxe2x80x9d that serves as the subnet""s gateway router. As is known in the art, the gateway connects computer networks using different networking protocols or operating at different transmission capacities. As is known in the art, a router translates differences between network protocols and routes data packets to an appropriate network node or network device.
When a mobile node xe2x80x9croams,xe2x80x9d (i.e., dynamically changes its physical location), it periodically transmits xe2x80x9cagent solicitationxe2x80x9d messages to other gateway routers. A mobile node also listens for xe2x80x9cagent advertisementxe2x80x9d messages from other gateway routers. When a mobile node receives an agent advertisement message indicating that it is now on a foreign subnet, it registers with the foreign gateway router or xe2x80x9cforeign agentxe2x80x9d and its home agent. The registration with the home agent indicates the mobile node is away from xe2x80x9chomexe2x80x9d (i.e., away from its home subnet). The registration with the foreign agent allows the mobile node to receive data on the foreign subnet.
The Mobile Internet Protocol allows a mobile node to dynamically change its network connectivity in a manner that is transparent to protocol layers above the Internet Protocol layer. For example, without re-establishing Transmission Control Protocol or User Datagram Protocol sessions.
As is known in the art, Transmission Control Protocol (xe2x80x9cTCPxe2x80x9d) and User Datagram Protocol (xe2x80x9cUDPxe2x80x9d) are often used over IP in computer networks. Transmission Control Protocol provides a connection-oriented, end-to-end reliable protocol designed to fit into a layered hierarchy of protocols that support multi-network applications. User Datagram Protocol provides a transaction oriented datagram protocol, where delivery and duplicate packet protection are not guaranteed.
It is often desirable to establish a voice, video and/or data call from a mobile network device that has roamed from its home network to a foreign network. Such a voice or data call is typically established using a call control protocol such as Session Initiation Protocol (xe2x80x9cSIPxe2x80x9d), H.323 and others.
However, there are several problems associated with using Mobile IP from a mobile network node to establish a communications path that includes a voice, video and/or data call. One problem is that round-trip routing to and from a mobile node is typically asymmetric and follows a triangular routing path.
A correspondent with a router receives data packets for the mobile node from an external network such as the Internet. The correspondent is, for example, a network access service provider being used by mobile node. The correspondent sends data packets for the mobile node to the mobile node""s home agent.
The home agent creates a xe2x80x9cvirtual tunnelxe2x80x9d to the foreign agent via the external network. When the foreign agent receives tunneled packets, it removes the tunnel packet headers and routes them to the mobile node, which is currently registered on the foreign network.
When the mobile node sends packets to an external destination on external network, no tunneling is used. Data packets are transmitted from mobile node to the correspondent, completing a virtual routing triangle. Thus, the round-trip routing because of its asymmetric triangular path introduces round-trip time (xe2x80x9cRTTxe2x80x9d) delays for communications with the mobile node. Such round-trip time delays are undesirable for establishing voice, video or data calls.
Another problem is that whenever a mobile node using Mobile IP desires to establish a call, a number of different message sequence may be sent and received including Session Initiation Protocol (xe2x80x9cSIPxe2x80x9d), H.323, Authentication Authorization and Accounting (xe2x80x9cAAAxe2x80x9d) (e.g., for billing), Domain Name System (xe2x80x9cDNSxe2x80x9d) (e.g., for IP address decoding, etc.) requests and responses. These different message sequences, even though necessary to establish a voice, video or data call, also add additional round-trip time delays for establishing such a call.
Another problem is that whenever a mobile mode using Mobile IP makes call requests, a foreign call services application sends a response that currently must pass through a home agent on a home network for the mobile node, through a foreign agent on the foreign network and then to the mobile node on the foreign network. This adds at least one, but possible multiple extra round-trip time delay(s) to the transaction, depending on network configuration. Since calls, especially voice and video calls, must be established as quickly as possible in order to reduce post dial delay, satisfy human factors constraints, such as not irritating or confusing users due long call establishment delays, this extra round-trip time delay can present a significant problem for users.
This it is desirable to provide a method and system to reduce or eliminate extra round-trip time delays for voice, video or data calls on a mobile node that has roamed from a home network to a foreign network. The round-trip time delays should be reduced to optimize call setup as well as other communications to and from a mobile node using
In accordance with preferred embodiments of the present invention, some of the problems associated with establishing voice, video or data calls from mobile network devices are overcome. A method and system for tunnel optimized call setup for mobile nodes is presented.
One aspect of the invention includes a method and system for establishing and using a unidirectional virtual tunnel with foreign service applications (e.g., call service applications) on a foreign network. The unidirectional virtual tunnel overrides a default communications path from the foreign service applications on a foreign network to a home agent on a home network and to a mobile network device on the foreign network and creates a new communications path from the foreign service applications to a tunnel server on the foreign network, to the foreign agent and to the mobile network device on the foreign network. The method and system may help reduce the round-time trip delays encountered when trying to establish a voice, video or data call from a mobile device that has roamed from its home network to a foreign network.
The foregoing and other features and advantages of preferred embodiments of the present invention will be more readily apparent from the following detailed description. The detailed description proceeds with references to the accompanying drawings.